1. Field of the Invention
The present invention relates to a method for fabricating a pattern on a biosensor substrate and a biosensor using the same.
2. Description of the Related Art
A biosensor is an element that can selectively detect a substance to be analyzed by transducing biological interaction and recognition reaction into an electric or optical signal through a combination of a biological receptor having a recognition function of a specific substance with an electrical or optical transducer. Herein, the substance includes general chemicals in addition to biosubstances such as DNA and blood sugar. The biological receptor, as a biosubstance that serves to generate a signal measurable by the transducer while selectively recognizing the analyzed substance, includes enzyme, protein, DNA, cell, hormone, a biomembrane, a tissue, etc. Various physicochemical methods such as electrochemical, optical, magnetic, piezoelectric, electronic methods, etc. are adopted to transduce the generated biosignal or recognition reaction into useful signals, such that an electrical signal is ultimately obtained. The biosensor reversibly recognizes a specific substance to thereby enable successive measurement. The biosensor may include a biosensor that irreversibly recognizes the specific interaction like an antigen-antibody interaction or hybrid formation of DNA. Such biosensor that has a concept as a detector is classified into a biochip. However, recently, defining between the biosensor and the biochip has been ambiguous and technical compatibility therebetween is being actively progressed, such that the biosensor and the biochip are not particularly differentiated from each other.
Immobilizing bioactive compounds onto a specific spot of the biosensor is required to fabricate the biosensor. Most of the biosensors are constituted by a substrate, a chemical linker, and a biological interface. Glass, quartz, silicon wafer, or polymer is generally used as the substrate. However, these substrates do not have a specific binding characteristic for binding directly with the biosubstance. Therefore, modification of a surface is required in order to bind the substrate with the biological interface.
The chemical linker having the specific binding characteristic may be generated on or added to the surface of the substrate at the time of modifying the substrate itself or adding various reagents to an organic film. For surface modification, the related art is based on physical absorption, chemical binding, ligand-receptor binding, and a combination thereof. Selection of the art for achieving the above-mentioned object is based on a specific chemical or physical characteristic of the substrate and/or biological interface. Even though a lot of chemicals and materials are used for modifying the substrate, most of the materials and chemicals that function as the chemical linker must have bi-functionality to bind both the substrate and the biological interface.
Polyethylenimine (PEI) is one of the polymers used for achieving the above-mentioned object. The polymer may be used for immobilizing cells, DNAs, and proteins in addition to transfection of cell lines. PEI is the branched polymer having a high-density amine group. Pure PEI, which contains plural amines, may be covalently bound with other molecules such as succinimidyl ester, sulfonyl chloride, and isothiocyanate mainly used as a linker between the film and a bioactive compounds. Further, PEI is known to be immobilized onto a silicon oxide film through spontaneous absorption. These characteristics make PEI into a material suitable for modifying the surface.
In the related art, a technique using an etching process was used as a method of immobilizing the biosubstance by patterning. For example, in a method of immobilizing polypeptide onto the substrate by using a photolithography process, a mask having each pattern must be fabricated whenever fabricating a chip, and cleaning and mask arraying processes must be performed for each process. As a result, the process becomes complicated and expensive equipment is required, such that cost becomes high. Moreover, the related art was limitative in a pattern design and not environmentally-friendly.
In immobilizing the biosubstance onto the substrate, an immobilization rate of the biosubstance must be high and the biosubstance must be immobilized in a desired pattern (preferably, a minute pattern). In particular, it is more important to integrate and immobilize the biosubstance onto a specific spot of a micrometer scale with high density as possible. In the case in which the biosubstance is integrated with high density, the ability of deciphering genetic information is improved as much. However, in order to spot or apply the biosubstance to a very small spot of the sensor, a very expensive equipment such as a micro-arrayer is required. The reason for this is that a sensing element of the biosensor occupies the very small spot. Even though the entire sensor is large, the size of the spot is generally in the range of nm to μm. Therefore, development of a new method for immobilization or attachment is required.
As a result, the present inventors have completed the present invention by finding that the amine group on the PEI layer formed on the surface of the substrate is eliminated to lose a binding capability with succinimidyl ester by UN irradiation and that the surface of the substrate is patterned, and verifying a signal of a substance (i.e., streptavidin) selectively bounded with a biosubstance (i.e., biotin) that is immobilized onto the patterned surface.